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Exposure Limits (exposure + limit)

Distribution by Scientific Domains

Medical Sciences	72%
Mathematics and Statistics	11%

Kinds of Exposure Limits

occupational exposure limit

Selected Abstracts

Neuromotor effects of short-term and long-term exposures to trichloroethylene in workers,

AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 9 2010
Katsuyuki Murata MD
Abstract Background Health effects of long-term exposure to organic solvents at low levels are a major concern in industrialized countries. To assess the neuromotor impact of trichloroethylene objectively, static postural sway and hand tremor parameters, along with urinary trichloroethanol (TCOH) and trichloroacetic acid (TCAA) levels, were investigated in 57 workers without obvious neurological disorders and 60 control subjects. Methods The workers had been occupationally exposed to trichloroethylene for 0.1,37 years. The cumulative exposure index (CEI) was calculated from their occupational history and total trichloro-compounds (TCOH,+,TCAA). Results Median levels in the workers were 1.7,mg/L for TCOH and 2.5,mg/L for TCAA, and the maximum ambient trichloroethylene concentration was estimated to be <22,ppm from the previously reported equation using TCOH,+,TCAA. Sway parameters with eyes open and tremor intensity in dominant hand were significantly larger in the exposed workers than in the control subjects when adjusting for possible confounders. A significant dose,effect association was seen between two sway parameters and urinary TCOH level in the workers. Tremor intensities in non-dominant hand differed significantly among three groups of the workers divided according to the CEI. Conclusions These findings suggest that trichloroethylene exposure, even at low levels of less than the short-term exposure limit by the ACGIH, can affect the neuromotor function of workers. The postural instability appears to result from recent exposure, and the increased tremor may occur due to short-term and long-term exposures. Hereafter, such objective measures, along with subjective symptoms, should be carefully used for the occupational exposure limit setting. Am. J. Ind. Med. 53:915,921, 2010. © 2010 Wiley-Liss, Inc. [source]

Assessment of airborne and dermal exposure to 2-ethoxyethyl acetate in an occupational environment,

AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 8 2009
Tung-Sheng Shih ScD
Abstract Background Because of its chemical,physical properties, 2-ethoxyethyl acetate (EEAc) can penetrate through the skin. However, no actual occupational environmental studies or empirical dermal exposure measurements have been performed. Methods Twenty workers from a commercial label silk screening shop were recruited and they completed a questionnaire of demographic information. Environmental monitoring of EEAc exposure via respiratory and dermal routes was performed for five consecutive working days. Results Airborne EEAc concentration was over the permissible exposure limit of 5,ppm in 90% of the participants. The dermal EEAc concentration was highest on the palms. The EEAc concentration correlated with skin exposure level (P,<,0.001). The dermal EEAc concentrations in individuals who did not wear gloves were higher than in those who wore gloves. Conclusions EEAc on the skin is strongly associated with airborne EEAc. Wearing impermeable gloves during high-risk tasks (cleaning process) can reduce EEAc dermal exposure on the palms. Am. J. Ind. Med. 52:654,661, 2009. © 2009 Wiley-Liss, Inc. [source]

Urinary 1-hydroxypyrene concentrations in Chinese coke oven workers relative to job category, respirator usage, and cigarette smoking

AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 9 2007
Bo Chen PhD
Abstract Background 1-Hydroxypyrene (1-OHP) is a biomarker of recent exposure to polycyclic aromatic hydrocarbons (PAHs). We investigated whether urinary 1-OHP concentrations in Chinese coke oven workers (COWs) are modulated by job category, respirator usage, and cigarette smoking. Methods The present cross-sectional study measured urinary 1-OHP concentrations in 197 COWs from Coking plant I and 250 COWs from Coking plant II, as well as 220 unexposed referents from Control plant I and 56 referents from Control plant II. Results Urinary 1-OHP concentrations (geometric mean, µmol/mol creatinine) were 5.18 and 4.21 in workers from Coking plants I and II, respectively. The highest 1-OHP levels in urine were found among topside workers including lidmen, tar chasers, and whistlers. Benchmen had higher 1-OHP levels than other workers at the sideoven. Above 75% of the COWs exceeded the recommended occupational exposure limit of 2.3 µmol/mol creatinine. Respirator usage and increased body mass index (BMI) slightly reduced 1-OHP levels in COWs (P,<,0.1). Cigarette smoking significantly increased urinary 1-OHP levels in unexposed referents (P,<,0.005), but had no effect in COWs (P,>,0.1). Conclusions Chinese COWs, especially topside workers and benchmen, are exposed to high levels of PAHs. Urinary 1-OHP concentrations appear to be modulated by respirator usage and BMI in COWs, as well as by smoking in unexposed referents. Am. J. Ind. Med. 50:657,663, 2007. © 2007 Wiley-Liss, Inc. [source]

Metal and non-metal miners' exposure to crystalline silica, 1998,2002

AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 7 2006
James L. Weeks ScD
Abstract Background Crystalline silica is well known to cause silicosis and other diseases. Exposure is common in the mining industry and consequently, the US Mine Safety and Health Administration (MSHA) evaluates miners exposure to silica to determine compliance with its exposure limit. Methods MSHA exposure measurements were obtained for the 5-year period from 1998 to 2002 and average exposure was calculated classified by occupation and by mine. Evaluation criteria were whether average values exceeded MSHA's permissible exposure limit or the limit recommended by the National Institute for Occupational Safety and Health (NIOSH), whether there was a risk of exposure to freshly fractured silica, and whether there was a risk of a high rate of exposure to silica. Results Miners in certain jobs are exposed to silica above permissible and recommended exposure limits. Some miners may also be exposed at a high rate or to freshly fractured silica. Conclusions Known dust control methods should be implemented and regular medical surveillance should be provided. Am. J. Ind. Med. 49:523,534, 2006. © 2006 Wiley-Liss, Inc. [source]

Hypersensitivity pneumonitis due to metal working fluids: Sporadic or under reported?

AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 6 2006
Amit Gupta MD
Abstract Background Occupational exposure to metal working fluids (MWF) is common with over 1.2 million workers in the United States involved in machine finishing, machine tooling, and other metalworking operations. MWF is a known cause of hypersensitivity pneumonitis (HP). Recent reports of outbreaks of hypersensitivity HP secondary to exposure to MWF are reported. Design Cases were identified through the Occupational Disease surveillance system in the State of Michigan and from referrals for evaluation to the Division of Occupational and Environmental Medicine at Michigan State University (MSU). Each patient underwent a clinical examination including an occupational history, lung function studies, radiographic imaging, and in some cases lung biopsies. Following the diagnosis of definite HP, an industrial hygiene investigation was carried out, which included a plant walk-through, and review of the "Injury and Illness" log. Air monitoring and microbial sampling results were reviewed. Results As part of Michigan's mandatory surveillance system for occupational illnesses, seven cases of suspected HP were identified in 2003,2004 from three facilities manufacturing automobile parts in Michigan. Each plant used semi-synthetic MWFs, and conducted a MWF management program including biocide additions. Two facilities had recently changed the MWF before the cases arose. Growth of mycobacteria was found in these two MWFs. Breathing zone samples for particulates of two employees in plant A (two cases) ranged from 0.48 to 0.56 mg/m3. In plant B (four cases), two employees' sampling results ranged from 0.10 to 0.14 mg/m3. No air sampling data were available from plant C. Conclusion Hypersensitivity pneumonitis due to exposure to MWFs is under-recognized by health care providers, and current surveillance systems are inadequate to provide a true estimate of its occurrence. HP arose from environments with exposures well below the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for MWF, and in one case from exposures well below the National Institute of Occupational Safety and Health (NIOSH) recommended exposure limit (REL). The sporadic nature of reports of HP in relationship to MWF probably represents a combination of workplace changes that cause the disease and inadequate recognition and reporting of the disease when it does occur. Physician awareness of HP secondary to MWF and an effective medical surveillance program are necessary to better understanding the epidemiology and prevention of this disease. Am. J. Ind. Med. 2006. © 2006 Wiley-Liss, Inc. [source]

A Note on Comparing Exposure Data to a Regulatory Limit in the Presence of Unexposed and a Limit of Detection

BIOMETRICAL JOURNAL, Issue 6 2005
Haitao Chu
Abstract In some occupational health studies, observations occur in both exposed and unexposed individuals. If the levels of all exposed individuals have been detected, a two-part zero-inflated log-normal model is usually recommended, which assumes that the data has a probability mass at zero for unexposed individuals and a continuous response for values greater than zero for exposed individuals. However, many quantitative exposure measurements are subject to left censoring due to values falling below assay detection limits. A zero-inflated log-normal mixture model is suggested in this situation since unexposed zeros are not distinguishable from those exposed with values below detection limits. In the context of this mixture distribution, the information contributed by values falling below a fixed detection limit is used only to estimate the probability of unexposed. We consider sample size and statistical power calculation when comparing the median of exposed measurements to a regulatory limit. We calculate the required sample size for the data presented in a recent paper comparing the benzene TWA exposure data to a regulatory occupational exposure limit. A simulation study is conducted to investigate the performance of the proposed sample size calculation methods. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A Mixture Model for Occupational Exposure Mean Testing with a Limit of Detection

BIOMETRICS, Issue 3 2001
Douglas J. Taylor
Summary. Information from detectable exposure measurements randomly sampled from a left-truncated log-normal distribution may be used to evaluate the distribution of nondetectable values that fall below an analytic limit of detection. If the proportion of nondetects is larger than expected under log normality, alternative models to account for these unobserved data should be considered. We discuss one such model that incorporates a mixture of true zero exposures and a log-normal distribution with possible left censoring, previously considered in a different context by Moulton and Halsey (1995, Biometrics51, 1570,1578). A particular relationship is demonstrated between maximum likelihood parameter estimates based on this mixture model and those assuming either left-truncated or left-censored data. These results emphasize the need for caution when choosing a model to fit data involving nondetectable values. A one-sided likelihood ratio test for comparing mean exposure under the mixture model to an occupational exposure limit is then developed and evaluated via simulations. An example demonstrates the potential impact of specifying an incorrect model for the nondetectable values. [source]

Setting workplace exposure limits: An important stewardship function

ENVIRONMENTAL QUALITY MANAGEMENT, Issue 2 2004
Ernest D. Weiler
First page of article [source]

Personnel breathing zone sevoflurane concentration adherence to occupational exposure limits in conjunction with filling of vaporisers

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2010
H. HEIJBEL
Background: Work place pollution during filling of anaesthetic vaporisers has been a matter of concern. We studied personnel breathing zone ambient air sevoflurane concentrations during filling of sevoflurane with three different filling systems: Quik-FilÔ for Abbott and Dräger FillÔ resp. Easy-FilÔ adapters for Baxter sevoflurane bottles, referred to as ,Abbott and Baxter filling systems'. Method: Sequential filling of three vaporisers was performed for a 15-min period, once with each of Abbott and Baxter filling systems, by four nurses. Ambient-air sevoflurane p.p.m. concentration in the breathing zone was continuously measured using a Miran 1a device during filling, and the mean 15 min sevoflurane concentration was calculated. Results: All eight measured (4 × 2 sequences) 15-min mean breathing zone sevoflurane concentrations covering filling of three vaporisers were well below the recommended short-term value (STV) provided by the Swedish Work Environment Authority (STV 20 p.p.m.). Conclusion: The breathing zone sevoflurane concentration during filling of sevoflurane with Baxter or Abbott filling systems, in an ordinary operating theatre, was found to be reassuringly below the Swedish recommended STV (20 p.p.m. average for a 15-min period). [source]

Reassessment of occupational exposure limits

AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 6 2008
Hans Stouten MSc
Abstract Background Although the Netherlands currently has its own procedure for evaluating chemical compounds and setting occupational exposure limits (OELs), most of these limits were originally adopted in the 1970s from threshold limit values (TLVs) set by the American Conference of Governmental Industrial Hygienists (ACGIH). However, beginning in the late 1980s, criticism about non-scientific considerations being used to set TLV's suggested that TLVs might not offer sufficient health protection to workers. This situation prompted the Dutch Ministry of Social Affairs and Employment to request that the Health Council of the Netherlands reassess the health protection of MAC values that were contained in the 1994 Dutch MAC list. Methods Criteria documents were prepared for 161 compounds. They were evaluated by a committee of the Health Council of the Netherlands consisting of international experts who reassessed the toxicological hazards of these substances and recommended, whenever possible, health-based OELs. The results of the reassessment by the Health Council were compared with the MAC values of the 1994 Dutch MAC list, ACGIH TLVs, and existing German OELs. Results The toxicological database met the committee's criteria for a health-based OEL for only about 40% of the compounds. Conclusions Many older MAC values were either too high or not scientifically supported and therefore not health-based. Am. J. Ind. Med. 51:407,418, 2008. © 2008 Wiley-Liss, Inc. [source]

Total imprecision of exposure biomarkers: implications for calculating exposure limits

AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 10 2007
Philippe Grandjean MD
Abstract Background Assessment of the imprecision of exposure biomarkers usually focuses on laboratory performance only. Unrecognized imprecision leads to underestimation of the true toxicity of the exposure. We have assessed the total imprecision of exposure biomarkers and the implications for calculation of exposure limits. Methods In a birth cohort study, mercury concentrations in cord blood, cord tissue, and maternal hair were used as biomarkers of prenatal methylmercury exposure. We determined their mutual correlations and their associations with the child's neurobehavioral outcome variables at age 7 years. With at least three exposure parameters available, factor analysis and structural equation modeling could be applied to determine the total imprecision of each biomarker. The estimated imprecision was then applied to adjust benchmark dose calculations and the derived exposure limits. Results The exposure biomarkers correlated well with one another, but the cord blood mercury concentration showed the best associations with neurobehavioral deficits. Factor analysis and structural equation models showed a total imprecision of the cord-blood parameter of 25,30%, and almost twice as much for maternal hair. These imprecisions led to inflated benchmark dose levels. Adjusted calculations resulted in an exposure limit 50% below the level recommended by the U.S. National Research Council. Conclusions The biomarker imprecisions of 25,50% much exceeded normal laboratory variability. Such imprecision causes underestimation of dose-related toxicity and therefore must be considered in the data analysis and when deriving exposure limits. Future studies should ideally include at least three exposure parameters to allow independent assessment of total imprecision. Am. J. Ind. Med. 50:712,719, 2007. © 2007 Wiley-Liss, Inc. [source]

Metal and non-metal miners' exposure to crystalline silica, 1998,2002

Analyzing digital vector waveforms of 0,3000,Hz magnetic fields for health studies,

BIOELECTROMAGNETICS, Issue 5 2010
Joseph D. Bowman
Abstract To improve the assessment of magnetic field exposures for occupational health studies, the Multiwave® System III (MW3) was developed to capture personal exposures to the three-dimensional magnetic field vector B(t) in the 0,3000,Hz band. To process hundreds of full-shift MW3 measurements from epidemiologic studies, new computer programs were developed to calculate the magnetic field's physical properties and its interaction with biological systems through various mechanisms (magnetic induction, radical pair interactions, ion resonance, etc.). For automated calculations in the frequency domain, the software uses new algorithms that remove artifacts in the magnetic field's Fourier transform due to electronic noise and the person's motion through perturbations in the geomagnetic field from steel objects. These algorithms correctly removed the Fourier transform artifacts in 92% of samples and have improved the accuracy of frequency-dependent metrics by as much as 3300%. The output of the MwBatch software is a matrix of 41 exposure metrics calculated for each 2/15,s sample combined with 8 summary metrics for the person's full-period exposure, giving 294 summary-exposure metrics for each person monitored. In addition, the MwVisualizer software graphically explores the magnetic field's vector trace, its component waveforms, and the metrics over time. The output was validated against spreadsheet calculations with pilot data. This software successfully analyzed full-shift MW3 monitoring with 507 electric utility workers, comprising over 1 million vector waveforms. The software's output can be used to test hypotheses about magnetic field biology and disease with biophysical models and also assess compliance with exposure limits. Bioelectromagnetics 31:391,405, 2010. © 2010 Wiley-Liss, Inc. [source]

Extremely low frequency (ELF) electric and magnetic field exposure limits: Rationale for basic restrictions used in the development of an Australian standard,

BIOELECTROMAGNETICS, Issue 6 2008
Andrew W. Wood
Abstract There are large disparities between basic restrictions for exposure to extremely low-frequency (0,3 kHz) Electric and Magnetic Fields set by two major international bodies. Both bodies agree that these basic restrictions should prevent neuro-stimulatory effects: the retinal phosphene at frequencies up to a few hundred Hertz and peripheral nervous stimulation (PNS) at higher frequencies. The disparity arises from differences in estimated thresholds and frequency dependence, and whether restrictions should be of tissue induced current density or electric field. This paper argues that the latter metric more directly relates to neurostimulatory processes. By analysing available literature, a threshold for retinal phosphenes occurrence is found to be 56 mV/m (95% Confidence Interval 2,1330 mV/m), with a characteristic frequency of 20 Hz. Similarly, the smallest PNS sensation threshold is identified at 2 V/m (characteristic frequency above 3 kHz). In the case of the former, the large range of uncertainty suggests a ,power of ten' value of 100 mV/m. For the latter, because of the small margin between sensation and pain threshold, and because of the large individual variation, the smallest estimate of sensation threshold (2 V/m) represents a basic restriction with precaution incorporated. Bioelectromagnetics 29:414,428, 2008. © 2008 Wiley-Liss, Inc. [source]